-LRB- CNN -RRB- -- Mitt Romney has won the New Hampshire primary . That much was clear as soon as the polls closed Tuesday night . It took a little while longer to sort out exactly where the other candidates finished behind him , but that barely matters . Regardless of the other candidates ' performances in New Hampshire or even what happens in the South Carolina primary next week , Mitt Romney is extremely likely to be the Republican nominee .

How can we know this so early , after only one primary election and the Iowa caucus ? The dominant political science explanation of the presidential nominating process is contained in the book , `` The Party Decides '' by Marty Cohen , David Karol , Hans Noel , and John Zaller . They point out that candidates need support from their party 's politicians and activists across the country .

From 1980 to the present , no candidate who significantly trailed in party endorsements has won the nomination . A few candidates have been nominated in years when no candidate took an early endorsement lead . These include Mike Dukakis in 1988 and Barack Obama in 2008 . But no candidate has succeeded when significantly trailing by that measure .

There are reasons to believe that this pattern is not a coincidence . Your party 's politicians and activists can help you organize and raise money as you hopscotch to primaries and caucuses across the country . On top of this is the effect of national media figures on TV , radio and the Internet closing ranks around the candidate most leaders in their party support .

We got an excellent example of this in December when Newt Gingrich opened up a fairly large lead in Iowa and national polls . Romney 's supporters used his fundraising advantage to pummel -LRB- through a sympathetic super-PAC -RRB- Gingrich with negative ads . On top of this , Republican pundits almost universally condemned Gingrich .

As Ben Smith of Politico noticed , on December 14 , just about all columnists on the Washington Post op-ed page , regardless of their ideologies , criticized Gingrich .

On his morning show on MSNBC , former Republican congressman Joe Scarborough , who served with Gingrich in the 1990s , called him a `` bad person '' who `` will destroy our party . '' This would continue if someone like Gingrich had initial success in the primaries and caucuses .

As chronicled by Nate Silver , Mitt Romney now has a big lead in Republican Party endorsements , giving him a huge advantage moving forward . Through the end of November , Romney had 55 % of all Republican endorsements and his share has only increased in December and after his slim victory over Santorum in Iowa . The only other person with a non-trivial number of endorsements is Texas Gov. Rick Perry . Consequently , Perry remains the only candidate who could somewhat plausibly challenge Romney in a drawn out fight for the nomination .

How did this happen ? How did a candidate who relatively recently supported abortion and gay rights , and who as governor passed a health reform bill remarkably similar to the president 's , manage to lock up the Republican establishment 's support ? It was n't inevitable . The most plausible alternatives were former Minnesota Gov. Tim Pawlenty and Perry .

Pawlenty likely miscalculated by dropping out after weak performances in debates and in the Iowa straw poll . Pawlenty 's campaign was low on cash . But many Republican endorsers were late in deciding to go with Romney . If Pawlenty had laid off campaign staff but stayed in the race , he might have benefited from a late surge in endorsements and in the polls . -LRB- Pawlenty 's mediocre debating performances would have evoked Cicero in comparison to Perry . -RRB-

Which brings us to the second candidate who could have won support from Republican elites : Perry . Right after he announced , it appeared that he might be able to match or even surpass Romney in establishment backing . But he has been hurt by his extremely weak campaign skills , including disastrous performances in debates and on the stump .

In Republican eyes , he may be a reliable conservative , but he appears to be someone incapable of running a competent campaign against Barack Obama . Still , Perry remains the only candidate besides Romney with nontrivial support from Republican elites . If he could somehow manage to run a respectable campaign and win a substantial number of votes in South Carolina , he would be Romney 's only halfway plausible threat .

The opinions expressed in this commentary are solely those of Jonathan Ladd .

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Jonathan Ladd : It 's a good bet that Mitt Romney will win the GOP nomination

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He says we can make that judgment based on his support among party insiders

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Candidates with the endorsement of party elites have typically won the nomination

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Ladd : The only candidate who even approaches Romney 's party endorsements is Perry